Some updates on "speed and feed" and the mill chattering
 

One is a very highly embarrassing confession. Along the lines of
Gunner's own trailer tire passing him by at the red light.

The mill, as I mentioned, was chattering under what I considered to be
moderate cuts. I wondered how come it was chattering.

Now I know why: The head is attached to the rigid ram by means of four
socket head cap screws. And when installing the head, in general
excitement, I forgot to tighten them. So the head moved somewhat under
loads in X direction. Very embarrassing and humbling.

With that fixed, the mill is no longer chattering.

I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.

i

Some updates on "speed and feed" and the mill chattering
 

Ignoramus29468 wrote:

One is a very highly embarrassing confession. Along the lines of
Gunner's own trailer tire passing him by at the red light.

The mill, as I mentioned, was chattering under what I considered to be
moderate cuts. I wondered how come it was chattering.

Now I know why: The head is attached to the rigid ram by means of four
socket head cap screws. And when installing the head, in general
excitement, I forgot to tighten them. So the head moved somewhat under
loads in X direction. Very embarrassing and humbling.

With that fixed, the mill is no longer chattering.

I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.

i

Odd. Worn out switch that teeters on the edge of tripping? RFI/EMI from
the VFD leads to the spindle motor too close to the limit switch leads
and the interference gets stronger as you put some load on the motor?
Limit switch connection somewhere vibrating loose?

Some updates on "speed and feed" and the mill chattering
 

"Pete C." wrote:

Ignoramus29468 wrote:

One is a very highly embarrassing confession. Along the lines of
Gunner's own trailer tire passing him by at the red light.

The mill, as I mentioned, was chattering under what I considered to be
moderate cuts. I wondered how come it was chattering.

Now I know why: The head is attached to the rigid ram by means of four
socket head cap screws. And when installing the head, in general
excitement, I forgot to tighten them. So the head moved somewhat under
loads in X direction. Very embarrassing and humbling.

With that fixed, the mill is no longer chattering.

I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.

i

Odd. Worn out switch that teeters on the edge of tripping? RFI/EMI from
the VFD leads to the spindle motor too close to the limit switch leads
and the interference gets stronger as you put some load on the motor?
Limit switch connection somewhere vibrating loose?

Further on this, check "debounce interval" or equivalent settings for
your limit switch inputs, adjusting that higher can give more noise
immunity. You can also put some small bypass capacitors across the
inputs, I had a similar issue and putting a 0.1uf cap across the line
killed the noise.

Some updates on "speed and feed" and the mill chattering
 

On 2010-08-26, Pete C. wrote:

"Pete C." wrote:

Ignoramus29468 wrote:

One is a very highly embarrassing confession. Along the lines of
Gunner's own trailer tire passing him by at the red light.

The mill, as I mentioned, was chattering under what I considered to be
moderate cuts. I wondered how come it was chattering.

Now I know why: The head is attached to the rigid ram by means of four
socket head cap screws. And when installing the head, in general
excitement, I forgot to tighten them. So the head moved somewhat under
loads in X direction. Very embarrassing and humbling.

With that fixed, the mill is no longer chattering.

I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.

i

Odd. Worn out switch that teeters on the edge of tripping? RFI/EMI from
the VFD leads to the spindle motor too close to the limit switch leads
and the interference gets stronger as you put some load on the motor?
Limit switch connection somewhere vibrating loose?

Further on this, check "debounce interval" or equivalent settings for
your limit switch inputs, adjusting that higher can give more noise
immunity. You can also put some small bypass capacitors across the
inputs, I had a similar issue and putting a 0.1uf cap across the line
killed the noise.

Pete, I am not yet sure how to think about it, but I will try to get
to it. Right now all limits are wired in series. I may want to change
them and wire them as separate inputs to EMC, so that at least I will
know what tripped.

Putting a little cap and perhaps a resistor across the line would
probably help if is was a noise issue.

I know that VFD is mounted next to the motor and the cable from VFD to
motor, IIRC, does not touch any of the limit switch cables. But I will
check this.

i

Some updates on "speed and feed" and the mill chattering
 

Ignoramus29468 wrote:


With that fixed, the mill is no longer chattering.

No need to be embarrassed, it happens.
I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.
I'd be more likely to believe electrical noise, from either the spindle
VFD or the servo drive. Both use PWM, and produce high-voltage pulses
with sharp rise and fall times. These pulses may get stronger under
greater mechanical load.

Are you sure it is a limit switch error and not a following error?

Jon

Some updates on "speed and feed" and the mill chattering
 

On Thu, 26 Aug 2010 11:02:55 -0500, Ignoramus29468
wrote:

On 2010-08-26, Pete C. wrote:

"Pete C." wrote:

Ignoramus29468 wrote:

One is a very highly embarrassing confession. Along the lines of
Gunner's own trailer tire passing him by at the red light.

The mill, as I mentioned, was chattering under what I considered to be
moderate cuts. I wondered how come it was chattering.

Now I know why: The head is attached to the rigid ram by means of four
socket head cap screws. And when installing the head, in general
excitement, I forgot to tighten them. So the head moved somewhat under
loads in X direction. Very embarrassing and humbling.

With that fixed, the mill is no longer chattering.

I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.

i

Odd. Worn out switch that teeters on the edge of tripping? RFI/EMI from
the VFD leads to the spindle motor too close to the limit switch leads
and the interference gets stronger as you put some load on the motor?
Limit switch connection somewhere vibrating loose?

Further on this, check "debounce interval" or equivalent settings for
your limit switch inputs, adjusting that higher can give more noise
immunity. You can also put some small bypass capacitors across the
inputs, I had a similar issue and putting a 0.1uf cap across the line
killed the noise.

Pete, I am not yet sure how to think about it, but I will try to get
to it. Right now all limits are wired in series. I may want to change
them and wire them as separate inputs to EMC, so that at least I will
know what tripped.

I think we suggested that early on....G

Putting a little cap and perhaps a resistor across the line would
probably help if is was a noise issue.

I know that VFD is mounted next to the motor and the cable from VFD to
motor, IIRC, does not touch any of the limit switch cables. But I will
check this.

i


I am the Sword of my Family
and the Shield of my Nation.
If sent, I will crush everything you have built,
burn everything you love,
and kill every one of you.
(Hebrew quote)

Some updates on "speed and feed" and the mill chattering
 

On 2010-08-26, Jon Elson wrote:
Ignoramus29468 wrote:


With that fixed, the mill is no longer chattering.

No need to be embarrassed, it happens.
I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.
I'd be more likely to believe electrical noise, from either the spindle
VFD or the servo drive. Both use PWM, and produce high-voltage pulses
with sharp rise and fall times. These pulses may get stronger under
greater mechanical load.

Are you sure it is a limit switch error and not a following error?

I am positive that it is a limit switch error.

I sort of agree with your explanation about electrical noise.

I tend to blame the wires from servo amps. I do use twisted pairs, but
maybe I did a bad job somewhere.

i
The wires to

Some updates on "speed and feed" and the mill chattering
 

On Thu, 26 Aug 2010 18:51:13 -0500, Ignoramus29468
wrote:

On 2010-08-26, Jon Elson wrote:
Ignoramus29468 wrote:


With that fixed, the mill is no longer chattering.

No need to be embarrassed, it happens.
I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.
I'd be more likely to believe electrical noise, from either the spindle
VFD or the servo drive. Both use PWM, and produce high-voltage pulses
with sharp rise and fall times. These pulses may get stronger under
greater mechanical load.

Are you sure it is a limit switch error and not a following error?

I am positive that it is a limit switch error.

I sort of agree with your explanation about electrical noise.

I tend to blame the wires from servo amps. I do use twisted pairs, but
maybe I did a bad job somewhere.

i
Can i ask how its wired in EMC? The limits switches on my control use
24 volt DC and are wired NC to an opto isolator. This is a very noise
resistant design. I'm curious if you can do the same in EMC.

Karl

Some updates on "speed and feed" and the mill chattering
 

On Thu, 26 Aug 2010 18:51:13 -0500, Ignoramus29468
wrote:

On 2010-08-26, Jon Elson wrote:
Ignoramus29468 wrote:


With that fixed, the mill is no longer chattering.

No need to be embarrassed, it happens.
I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.
I'd be more likely to believe electrical noise, from either the spindle
VFD or the servo drive. Both use PWM, and produce high-voltage pulses
with sharp rise and fall times. These pulses may get stronger under
greater mechanical load.

Are you sure it is a limit switch error and not a following error?

I am positive that it is a limit switch error.

So have you individualized them yet, Ig? If not, do so and try the
same cut. Let us know if it still errors out.


I sort of agree with your explanation about electrical noise.

I tend to blame the wires from servo amps. I do use twisted pairs, but
maybe I did a bad job somewhere.

Twisted pairs will certainly limit noise transmittal.


I'm waaaay behind you.
My sister got the -other- book for me on the re-purchase, and I think
I'll be happier with it. I'm just getting into it now. The info is
very basic (so far), but that reinforces info I've learned here. It
does not follow the programming style "cookbook".
http://fwd4.me/b47 _The CNC Cookbook_, E Hess.

I'll be getting Overby's book when it releases, too.
http://fwd4.me/b46 _CNC Machining Handbook: Building, Programming, and
Implementation_, Alan Overby (of Custom CNC, Inc. fame, high-perf
ShopBot controllers)

--
Not merely an absence of noise, Real Silence begins
when a reasonable being withdraws from the noise in
order to find peace and order in his inner sanctuary.
-- Peter Minard

Some updates on "speed and feed" and the mill chattering
 

The following statement sounds like the prelude to many more posts regarding
problems (real or imagined) that might've been eliminated by following some
knowledgeable advice of adding a capacitor to the signal lines to see if a
problem might be noise-related.

*** "I am not an electrical engineer, unfortunately, but I wonder if a
capacitor and a small resistor could help with noise suppression." ***

IIRC, the advice was to use a small-value capacitor.. with the resistor
being interjected by the OP.

--
WB
..........


"Ignoramus29468" wrote in message
...
On 2010-08-27, Larry Jaques wrote:
On Thu, 26 Aug 2010 18:51:13 -0500, Ignoramus29468
wrote:

On 2010-08-26, Jon Elson wrote:
Ignoramus29468 wrote:


With that fixed, the mill is no longer chattering.

No need to be embarrassed, it happens.
I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.
I'd be more likely to believe electrical noise, from either the spindle
VFD or the servo drive. Both use PWM, and produce high-voltage pulses
with sharp rise and fall times. These pulses may get stronger under
greater mechanical load.

Are you sure it is a limit switch error and not a following error?

I am positive that it is a limit switch error.

So have you individualized them yet, Ig? If not, do so and try the
same cut. Let us know if it still errors out.

Not yet, no. I was making some chips today (a lot of)


I sort of agree with your explanation about electrical noise.

I tend to blame the wires from servo amps. I do use twisted pairs, but
maybe I did a bad job somewhere.

Twisted pairs will certainly limit noise transmittal.

I am not an electrical engineer, unfortunately, but I wonder if a
capacitor and a small resistor could help with noise suppression.

Some updates on "speed and feed" and the mill chattering
 

In article ,
Ignoramus29468 wrote:

[snip]

I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.

Or a lack of shielding on the cables. VFDs can generate a lot of hash.

For instance, the motor for the Millrite is fed by some stranded wire fed
through EMT conduit and Greenfield (flexible conduit) bought from Home Despot,
and the control pendant through 8-wire shielded signal cable.

On the lathe, only the control cable to the Reverse-Off-Forward switch is
shielded. The VFD to motor power cable is not shielded.

Putting a 0.1 uF film capacitor across the limit switch input to the controller
could also work, as others have suggested.

Joe Gwinn

Some updates on "speed and feed" and the mill chattering
 

Ignoramus29468 wrote:
I am positive that it is a limit switch error.

I sort of agree with your explanation about electrical noise.

I tend to blame the wires from servo amps. I do use twisted pairs, but
maybe I did a bad job somewhere.

Twisted pairs won't work on a PWM drive, where there are 80 V
transitions in a
couple hundred ns on one wire. The PWM transitions are not truly
differential, so
they don't cancel out. The dv/dt is huge on these things, so they act
as serious radio transmitters.
My own servo amps have L-C output filters to drastically cut down on the
EMI problem,
I am just amazed that so few other commercial units do this.

You could put ferrite cores over the wires, or use shielded cable either
on the motor
wires or the limit switch wires. I'm kind of surprised there is a
problem, as the digital inputs
on the PPMC DIO board are optoisolated, and those isolators are pretty slow.

Are you using normally open switch contacts? In that case, you have
open-circuit
wires acting as antennas. It would have been better for a few reasons
to use normally closed
contacts, so a dirty switch contact or broken wire would cause a
fail-safe condition. It would
also get rid of any floating-wire effects. Probably some capacitors to
ground would solve the
antenna problem.


Jon

Some updates on "speed and feed" and the mill chattering
 

Karl Townsend wrote:

Can i ask how its wired in EMC? The limits switches on my control use
24 volt DC and are wired NC to an opto isolator. This is a very noise
resistant design. I'm curious if you can do the same in EMC.

You can do ANYTHING in EMC. But, Igor is using my (Pico Systems) PPMC board
set. It has an isolated 5 V power supply (DC-DC converter) on the
digital I/O board,
and 16 general-purpose opto-isolated inputs. There is a default
assignment of these,
with a + limit, -limit and home switch assigned for each axis. So, a
3-axis machine
uses up 9 digital inputs. EMC2 provides different messages for each
limit tripped condition
(Machine is on + X limit switch). The default config file set will
inhibit motion past a limit
switch (except when homing and the HOME_IGNORE_LIMITS parameter is set
for that axis).

Of course, you can wire up any different gear you want, and connect it
to EMC's functions
however you choose, in either HAL or ClassicLadder.

All my servo amps have L-C output filters, so I just don't have this
sort of trouble with them.

Normally closed contacts are the best way to do things, as you say. The
way I have the
DIO board set up, and electronic sensor with NPN output can also be
used, but the DC-DC
converter doesn't have enough extra capacity to power the sensor itself,
just to sense the
output.

Jon

Some updates on "speed and feed" and the mill chattering
 

On Sat, 28 Aug 2010 09:32:09 -0700, Larry Jaques
wrote:


I am not an electrical engineer, unfortunately, but I wonder if a
capacitor and a small resistor could help with noise suppression.

First eliminate the known possible causes, then scope it to find out
if a nasty noise is actually present. Then ask an EE for help.

Having a proper ocilloscope helps a lot too.

Gunner


I am the Sword of my Family
and the Shield of my Nation.
If sent, I will crush everything you have built,
burn everything you love,
and kill every one of you.
(Hebrew quote)

Some updates on "speed and feed" and the mill chattering
 

On Sat, 28 Aug 2010 10:50:43 -0700, Gunner Asch
wrote:

On Sat, 28 Aug 2010 09:32:09 -0700, Larry Jaques
wrote:


I am not an electrical engineer, unfortunately, but I wonder if a
capacitor and a small resistor could help with noise suppression.

First eliminate the known possible causes, then scope it to find out
if a nasty noise is actually present. Then ask an EE for help.

Having a proper ocilloscope helps a lot too.

So what model are you going to be selling to him, Gunner? ;)

--
If we attend continually and promptly to the little that we can do,
we shall ere long be surprised to find how little remains that we
cannot do. -- Samuel Butler

Some updates on "speed and feed" and the mill chattering
 

On Sat, 28 Aug 2010 18:17:52 -0700, Larry Jaques
wrote:

On Sat, 28 Aug 2010 10:50:43 -0700, Gunner Asch
wrote:

On Sat, 28 Aug 2010 09:32:09 -0700, Larry Jaques
wrote:


I am not an electrical engineer, unfortunately, but I wonder if a
capacitor and a small resistor could help with noise suppression.

First eliminate the known possible causes, then scope it to find out
if a nasty noise is actually present. Then ask an EE for help.

Having a proper ocilloscope helps a lot too.

So what model are you going to be selling to him, Gunner? ;)


Since Ive got 5-7 or so...if he wants one..after he learns what he
needs, Id simply send him one for shipping and maybe a swap for
something.

But I dont have any storage scopes, which may be what is needed.



I am the Sword of my Family
and the Shield of my Nation.
If sent, I will crush everything you have built,
burn everything you love,
and kill every one of you.
(Hebrew quote)

Some updates on "speed and feed" and the mill chattering
 

On 2010-08-26, Pete C. wrote:

Ignoramus29468 wrote:

One is a very highly embarrassing confession. Along the lines of
Gunner's own trailer tire passing him by at the red light.

The mill, as I mentioned, was chattering under what I considered to be
moderate cuts. I wondered how come it was chattering.

Now I know why: The head is attached to the rigid ram by means of four
socket head cap screws. And when installing the head, in general
excitement, I forgot to tighten them. So the head moved somewhat under
loads in X direction. Very embarrassing and humbling.

With that fixed, the mill is no longer chattering.

I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.

i

Odd. Worn out switch that teeters on the edge of tripping? RFI/EMI from
the VFD leads to the spindle motor too close to the limit switch leads
and the interference gets stronger as you put some load on the motor?
Limit switch connection somewhere vibrating loose?

I have a sealed "RF filter". Would it make sense to connect it to the
power input of the VFD? Just for cleaner operation.

i

Some updates on "speed and feed" and the mill chattering
 

Are you using normally open switch contacts? In that case, you have
open-circuit wires acting as antennas. It would have been better
for a few reasons to use normally closed contacts, so a dirty switch
contact or broken wire would cause a fail-safe condition. It would
also get rid of any floating-wire effects. Probably some capacitors
to ground would solve the antenna problem.

It does not reoccur since I replaced the bad drive and routed motor
leads away from some wiring.

Some updates on "speed and feed" and the mill chattering
 

In article ,
Ignoramus24760 wrote:

On 2010-08-26, Pete C. wrote:

Ignoramus29468 wrote:

One is a very highly embarrassing confession. Along the lines of
Gunner's own trailer tire passing him by at the red light.

The mill, as I mentioned, was chattering under what I considered to be
moderate cuts. I wondered how come it was chattering.

Now I know why: The head is attached to the rigid ram by means of four
socket head cap screws. And when installing the head, in general
excitement, I forgot to tighten them. So the head moved somewhat under
loads in X direction. Very embarrassing and humbling.

With that fixed, the mill is no longer chattering.

I have one more weirdness: under heavier cuts, the mill triggers a
limit switch error for a reason that I cannot understand. But if I do
not push it quite as hard, it does not do so. I tend to think that it
is something related to the hardware of limit switches and maybe some
vibrations.

i

Odd. Worn out switch that teeters on the edge of tripping? RFI/EMI from
the VFD leads to the spindle motor too close to the limit switch leads
and the interference gets stronger as you put some load on the motor?
Limit switch connection somewhere vibrating loose?

I have a sealed "RF filter". Would it make sense to connect it to the
power input of the VFD? Just for cleaner operation.

Depends on just what this "RF Filter" is. Any more info available?

Joe Gwinn